Test the case when reg->smax_value is too small/big and can overflow,
and separately min and max values outside of stack bounds.
Example of output:
# ./test_verifier
#856/p indirect variable-offset stack access, unbounded OK
#857/p indirect variable-offset stack access, max out of bound OK
#858/p indirect variable-offset stack access, min out of bound OK
Signed-off-by: Andrey Ignatov <r...@fb.com>
---
.../testing/selftests/bpf/verifier/var_off.c | 57 ++++++++++++++++++-
1 file changed, 55 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/verifier/var_off.c
b/tools/testing/selftests/bpf/verifier/var_off.c
index f5d5ff18ef22..8504ac937809 100644
--- a/tools/testing/selftests/bpf/verifier/var_off.c
+++ b/tools/testing/selftests/bpf/verifier/var_off.c
@@ -40,7 +40,35 @@
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
- "indirect variable-offset stack access, out of bound",
+ "indirect variable-offset stack access, unbounded",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_2, 6),
+ BPF_MOV64_IMM(BPF_REG_3, 28),
+ /* Fill the top 16 bytes of the stack. */
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+ /* Get an unknown value. */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_1, offsetof(struct bpf_sock_ops,
+ bytes_received)),
+ /* Check the lower bound but don't check the upper one. */
+ BPF_JMP_IMM(BPF_JSLT, BPF_REG_4, 0, 4),
+ /* Point the lower bound to initialized stack. Offset is now in range
+ * from fp-16 to fp+0x7fffffffffffffef, i.e. max value is unbounded.
+ */
+ BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16),
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_10),
+ BPF_MOV64_IMM(BPF_REG_5, 8),
+ /* Dereference it indirectly. */
+ BPF_EMIT_CALL(BPF_FUNC_getsockopt),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R4 unbounded indirect variable offset stack access",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_SOCK_OPS,
+},
+{
+ "indirect variable-offset stack access, max out of bound",
.insns = {
/* Fill the top 8 bytes of the stack */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
@@ -60,7 +88,32 @@
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 5 },
- .errstr = "invalid stack type R2 var_off",
+ .errstr = "R2 max value is outside of stack bound",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_LWT_IN,
+},
+{
+ "indirect variable-offset stack access, min out of bound",
+ .insns = {
+ /* Fill the top 8 bytes of the stack */
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+ /* Get an unknown value */
+ BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
+ /* Make it small and 4-byte aligned */
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4),
+ BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 516),
+ /* add it to fp. We now have either fp-516 or fp-512, but
+ * we don't know which
+ */
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
+ /* dereference it indirectly */
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map_hash_8b = { 5 },
+ .errstr = "R2 min value is outside of stack bound",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
--
2.17.1
